Tuning of Activated Carbon for Solvent-Free Oxidation of Cyclohexane

Mohammad Sadiq,M Sohail Ahmad,Saima Sadiq,Haroon Ur Rashid,Muhammad Numan,Mashooq Khan,Razia Aman,Rahmat Ali,Muhammad Abid Zia,Saddam Hussain

doi:10.1155/2017/5732761

Abstract

Activated carbon (AC) was prepared from carbonization of phosphoric acid soaked peanut shell at 380°C under inert atmosphere followed by activation with hydrogen peroxide. The AC was characterized by SEM, EDX, FTIR, TGA, and BET surface area and pore size analyzer. The potential of AC as a catalyst for solvent-free oxidation of cyclohexane to cyclohexanol and cyclohexanone (the mixture is known as KA oil) in the presence of molecular oxygen at moderate temperature was investigated in a self-designed double-walled three-necked batch reactor. The effect of different reaction parameters/additive was optimized. The maximum productivity value (2.14 mmolg−1 h−1, without base, and 4.85 mmolg−1 h−1, with 0.2 mmol NaOH) of the desired product was achieved under optimal reaction parameters: vol 12.5 mL, cat 0.4 g, time 14 h, oxygen flow 40 mL/min (pO2 760 Torr), stirring 1100 rpm, and temp 75°C. The AC shows recyclability for multiple runs without any significant loss in activity. Thus, the AC can be an efficient catalyst, due to low cost, ease of synthesis, easy recovery, nonleaching, and recyclability for multiple uses for the solvent-free oxidation of cyclohexane.

Highlights

Activated carbon (AC) was reported as an effective catalyst for the first time in the beginning of 19th century [1]
Other catalytic formulations based on transition metals such as Cr, Co, Cu, Ta, and Nb have displayed only modest yields. Most of these catalysts have been utilized in the presence of a solvent [15, 16] and an expensive oxidant [17]. Several catalytic systems, such as FeRu, FeCo nanoclusters, supported Co catalyst, polymer supported cobaltous palmitate, and Co-salen complex immobilized on silica [18], Au/MCM-41 [13], gold nanoparticles immobilized upon mesoporous silica [19], Au nanoclusters on hydroxyapatite [17], metallophthalocyanines supported on γ-alumina [20], and chromium containing silicate [21], have been devised in solvent-free condition and presence of molecular oxygen
Activated carbon was synthesized by chemothermal process and used for solvent-free oxidation of cyclohexane at low temperature with molecular oxygen

Summary

Introduction

Activated carbon (AC) was reported as an effective catalyst for the first time in the beginning of 19th century [1]. Physicothermal, chemical, and chemothermal activation, the AC was tuned to show a good catalytic activity [4] in production of phosgene, sulphur halides, hydrogenation, polymerization, halogenation [5,6,7], removal of SO2 and NOx [8, 9], and oxidation of benzyl alcohol [10] This performance of AC was attributed to its porosity, active sites, and high surface area. Several catalytic systems, such as FeRu, FeCo nanoclusters, supported Co catalyst, polymer supported cobaltous palmitate, and Co-salen complex immobilized on silica [18], Au/MCM-41 [13], gold nanoparticles immobilized upon mesoporous silica [19], Au nanoclusters on hydroxyapatite [17], metallophthalocyanines supported on γ-alumina [20], and chromium containing silicate [21], have been devised in solvent-free condition and presence of molecular oxygen These catalysts in general have limitations of poor catalytic activity, loss of sensitivity, low selectivity, and high cost. The ease of preparation, sufficient activity, low cost, recyclability, nonleaching, and ecofriendly nature make AC a useful catalyst for solvent-free oxidation of cyclohexane

Experimental

Results and Discussion

Conclusion